1. Field of the Invention
The present invention relates to an arrangement to protect utility workers from explosions in manholes by isolating cables from personnel with a transparent structure.
2. Prior Art
Heretofore those of skill in the art have attempted to protect personnel with blankets of various forms and materials. Barrday Guard.RTM. produces a hydro blanket to cover live cables while others are being repaired. The blanket is made of an aramid material which is a carbon type of fiber. The hydro blanket can inhibit a fault blast once it is in place. Similar to the hydro blanket is the ArcSafe.TM. suppression blanket by workrite. The materials used in the ArcSafe.TM. blanket are Kevlar.RTM. and Nomex III.RTM. in thin layers. Thin layers make the blanket light and portable. Moreover, ArcSafe.TM. includes hook & loop fasteners to simplify holding the blanket in place. While being effective in containing most blasts from faults in the cabling, workers utilizing this type of protection are still subject to risks while installing the blankets prior to beginning repair work.
Alternative protection which theoretically protects a worker from electric shock and heat is protective clothing designed particularly for exposure to such hazards. Wearing this type of clothing eliminates the completely unprotected situation of the worker while installing a cover, but is necessarily cumbersome and does not protect the worker from impact and percussion force caused by a blast.
Theoretically a worker could protect himself fairly well by wearing a suit while installing a safety blanket, but a blast while entering or exiting a manhole could still be seriously detrimental to the workers well being. Furthermore, using both a suit and a blanket is impractical and compliance with regulations mandating such a combination of equipment would be unlikely. Therefore a strong need exists for a system which provides safety from blasts and yet allows inspection and repair of utility cables in a manhole. This need is compounded by Occupational Safety and Hazards Administration regulations and the criteria used to determine if a violation has occurred.